+2 it happens when the fish is feed a hi protein diet and feed to often or to much.
You can try some veggie based food soaked in Epsom salts and try feeding some green peas with the skins removed.
Yeah, that fish needs some help ASAP - when I kept mbuna I had good luck with the food soaked in epsom salts - could never get them to eat the green peas (skins removed).
I have to agree, like allot of people I know, that fish is full of s%^&t, treat as suggested, while this treatment can work great for fish, has no affect on people.